Fuel-injection pump for internal combustion engines

Abstract

A fuel-injection pump for internal combustion engines, particularly an in-line injection pump for diesel engine, with a control bore in the pump cylinder and with an upper control edge for determining the start of feed and an oblique spill edge for determining the end of feed. The pump piston is rotated about its longitudinal axis in order to set the desired feed quantity, for the purpose of achieving a better regulating behavior of the system as a whole, comprising the fuel-injection pump, feed-quantity regulator and internal-combustion engine. The spill edge is subdivided, along its run over a part of the circumference of the pump piston, into portions with different angles of inclination (α 1 , α 2 ) to the axis of the pump piston. The control-edge portion having the large angle of inclination (α 2 ) is located in the region of the pump piston which passes over the control bore during the pump-piston stroke in a rotary position of the pump piston for small feed quantities (lowered load range of the internal-combustion).

We claim: 
     
       1. An injection pump for an internal-combustion engine (1), comprising a pump piston (11) which is driven in a to-and-fro axial stroke movement in a pump cylinder (12) and which, by means of an end face (111), limits a pump working space (13) connected to a delivery conduit (14) and cooperates with at least one control bore (18, 19), connected to a fuel-filled suction space (20) and located in the pump cylinder (12), for determining the start of feed and end of feed, in such a way that an upper control edge (24) arranged on the end face (111) of the pump piston (11) determines the start of feed and a lower control edge (23), formed on an outer control groove (22) that extends obliquely over a part of a circumference of the pump piston (11) and constantly connected to the pump working space (13) determines the end of feed, and a feed-quantity regulating device (25) that rotates the pump piston (11) relative to the pump cylinder (12), the lower control edge (23) has, along its run, at least two portions (231, 232) with different angles of inclination (α 1 , α 2 ) to the axis (29) of the pump piston (11), and in that the control-edge portion (232) with a larger angle of inclination (α 2 ) is provided in the region of the pump piston (11) which passes over the control bore (18) during the pump-piston stroke in a rotary position of the pump piston (11) for small feed quantities that is a lower load range of an internal combustion engine, the upper control edge (24) is formed on a lower groove flank of a groove (31) which is open towards the end face (111) of the pump piston (11) and runs over a part of a circumference of the pump piston (11) and which, in the region of the pump piston (11) which passes over the control bore (18) during the pump-piston stroke in a rotary position assumed by the pump piston (11) in the case of small feed quantities, runs obliquely towards the edge of the end face (111). 
     
     
       2. An injection pump according to claim 1, in which the control groove (22) opens out on one side in an axial longitudinal groove (21) which is located in the pump piston (11) and which passes over the control bore (18) during the pump-piston stroke in a rotary position assumed by the pump piston (11) for a zero feed quantity, and the control-edge portion (232) of the lower control edge (23) having the large angle of inclination (α 2 ) is located directly at the longitudinal groove (21), and the further control-edge portion (231) follows the larger angle of inclination in the order of decreasing angles of inclination. 
     
     
       3. An injection pump according to claim 1, in which the oblique run in the upper control edge (24) is located near the longitudinal groove (21) and ends at a distance from the longitudinal groove (21) in the edge of the end face (111) of the pump piston (11). 
     
     
       4. An injection pump according to claim 2, in which the oblique run in the upper control edge (24) is located near the longitudinal groove (21) and ends at a distance from the longitudinal groove (21) in the edge of the end face (111) of the pump piston (11). 
     
     
       5. An injection pump according to claim 1, in which a delivery valve (14), which is designed as a constant-volume relief valve, is arranged between the pump working space (13) and the injection delivery conduit (15). 
     
     
       6. An injection pump according to claim 2, in which a delivery valve (14), which is designed as a constant-volume relief valve, is arranged between the pump working space (13) and the injection delivery conduit (15). 
     
     
       7. An injection pump according to claim 3, in which a delivery valve (14), which is designed as a constant-volume relief valve, is arranged between the pump working space (13) and the injection delivery conduit (15). 
     
     
       8. An injection pump according to claim 4, in which a delivery valve (14), which is designed as a constant-volume relief valve, is arranged between the pump working space (13) and the injection delivery conduit (15).